Which 49ers defensive player will have a bigger impact in 2026?

The 49ers will feature new contributors in 2026, and interest centers on whether Mykel Williams or Dre Greenlaw will have the bigger impact. Williams, a first-round pick in 2025, led San Francisco's defensive line in playing time during his rookie season after Nick Bosa was sidelined. He produced a 5.4% pressure rate on dropbacks, the second-lowest among edge rushers at that stage, yet his presence correlated with a 42% run-success rate and a 4.9% explosive run rate with him on the field. When he wasn't on the field those numbers worsened to 52.9% and 11.8% respectively. Meanwhile, Greenlaw signed with the Denver Broncos in March 2025 on a three-year deal worth up to $35 million, debuting in Week 7 and posting four run stuffs in a 27-snap game. His early performance established benchmarks among linebackers, as he posted strong run-tackle metrics during that period. San Francisco is adding two proven run-defenders to a unit that struggled against the ground game last season. The debate now centers on which defender will drive the 2026 unit more.